1. Field of the Invention
The present invention relates to a configuration of an active matrix type liquid crystal display integrated with a peripheral driving circuit.
2. Description of Related Art
Active matrix type liquid crystal displays have been known. They have a configuration in which an active matrix circuit and a peripheral driving circuit for driving the same circuit are integrated on a glass substrate or quartz substrate.
In such a liquid crystal panel integrated with a peripheral driving circuit, a thin film semiconductor that forms thin film transistors provided in the peripheral driving circuit must be a crystalline silicon thin film. The reason for this is that the peripheral driving circuit must operate at a high speed.
Reliability is an important consideration for a liquid crystal panel integrated with a peripheral driving circuit as described above. Specifically, what is important for such a device is the stability of image display in relation to the environment where it is used.
Especially, a crystalline silicon film has a problem in that it is significantly susceptible to the variation of characteristics with time and the influence of the environment where it is used because of the high level of characteristics of itself.
Specifically, a problem arises in that it is affected by stresses exerted thereon during the fabrication and handling of a liquid crystal panel and by moisture that permeates into the liquid crystal panel.
Further, a liquid crystal panel integrated with a peripheral driving circuit is designed in an intention to minimize the surface area of regions unnecessary for screen display. For example, efforts are put in minimizing the surface area occupied by the peripheral driving circuit.
Meanwhile, in a liquid crystal display, an encapsulating material for enclosing liquid crystal, referred to as "sealing material" is provided at a peripheral portion to hold liquid crystal between a pair of substrates.
As an effort to minimize the surface area of regions unnecessary for screen display as described above, the surface area occupied by the sealing material must be also reduced. A configuration for this purpose is known in which a sealing material is provided on a peripheral driving circuit to minimize the surface area excluding pixels (referred to as "frame").
In the case of an active matrix type liquid crystal display integrated with a peripheral driving circuit, faults that occur in the peripheral driving circuit can be a problem.
Especially, the configuration in which a sealing material is provided on a peripheral driving circuit to minimize the surface area excluding pixels (referred to as "frame") is subjected to more faults at the peripheral driving circuit.
This problem occurs due to the following reasons. A sealing material includes a kind of spacer referred to as "filler" for maintaining a gap between substrates.
In general, a peripheral driving circuit is at a high level of integration. As a result, thin film transistors and wiring lines located directly under such fillers are subjected to a pressure from the fillers (it is assumed that this pressure can be locally quite high) and are hence vulnerable to line breakage and poor contact.
Meanwhile, a spherical substrate gap maintaining means referred to as "spacer" is used also in an active matrix region. However, since an active matrix region is at a lower level of integration, faults attributable to the presence of a spacer are not as problematic as in a peripheral driving circuit.
It is an object of the invention disclosed in this specification to provide a configuration for an active matrix type liquid crystal display incorporating a peripheral driving circuit, in which the surface area excluding the region of a pixel matrix circuit is minimized.
On the basis of the above-described configuration, it is another object of the invention to provide a configuration that prevents breakage of thin film transistors provided on a peripheral driving circuit due to a pressure exerted by a sealing material.
It is still another object of the invention to provide a configuration for an active matrix type liquid crystal display incorporating a peripheral driving circuit, which prevents thin film transistors from being adversely affected by a stress exerted thereon during the fabrication and handling of the liquid crystal panel and which prevents moisture from permeating into the liquid crystal panel.